1) Field of the Invention
This invention relates to mechanisms designed to reduce the amount of dust emitted from a grain bin when grain from a truck or rail car is dumped into the grain bin.
2) Related Art
It is known to provide grain bins which receive grain dumped from a truck or rail car. These grain bins typically include a grate which forms a covering over the top opening of the grain bin. The truck is driven onto the grate such that the outlet of the truck is positioned over the grate, and the contents of the truck are emptied from the truck through the outlet. The grain being dumped from the truck falls through the grate and into the grain bin. The falling grain tends to generate a large amount of dust as it falls through the grate and into the bin. This dust tends to rush up through the grate and into the atmosphere as the falling grain displaces the air and dust within the bin. Several design efforts have been directed at reducing or eliminating the dust exiting the grain bin. One such mechanism designed to reduce emissions of dust from grain bins provides a plurality of vents positioned across the opening at the top of the grain bin. The vents are in a closed position until grain from the truck or rail car contacts the vents, at which time the vents open under the weight of the grain to allow the grain to fall into the bin. These mechanisms also include blower fans which suck air and dust from the grain bin in large quantities and direct the air and dust through a filter. The filter blocks the dust particles from passing into the atmosphere. These devices prevent a portion of the dust from entering the atmosphere. These devices tend not to function well when the filters become clogged, at which time the dust tends to boil upwardly through the vents and into the atmosphere. The filters and blower fans have the further disadvantage of requiring an undesirable amount of maintenance.
Also, these devices tend not to function in an acceptable manner when grain is dumped into the bin at relatively large flow rates. When grain is dumped from a truck through a small outlet door in the truck, the flow rate of grain being dumped is relatively low. Since the flow rate is low, the rate at which air is being displaced from the grain bin by the flow of dumped grain is also relatively low. The blower fans have large enough capacity to suck off the air and dust being displaced by the inflow of grain. But when relatively large flow rates of grain occur the rate at which air and dust is displaced by the inflow of grain correspondingly increases, and many prior art blower mechanisms are not large enough to accept the large rates of flow of displaced air and dust. These large flow rates are experienced, for example, when a truck is unloaded by tilting the bed of the truck upwardly and opening the entire rear wall or tailgate of the truck. Since the outlet of the truck is the entire rear wall or tailgate of the truck, the rate of flow of grain from the truck is relatively large in comparison to the rate of flow through a smaller outlet or opening in a wall of the truck.
Another dust reducing mechanism is described in detail in U.S. Pat. No. 5,544,686. That invention provides a plurality of metering units positioned across the opening in the top of the grain bin. The metering units include louvers that have open and closed positions. The metering units also include a sensor which senses the presence of the grain on the closed louvers. After the sensor senses the presence of grain on the closed louvers, a timer will operatively open the metering unit's louvers after a predetermined amount of time. The delay in opening the louver allows a pile of grain to accumulate on top of the louver before the louver opens. The quantity of grain on top of the louver is greater than can pass through the louver at one time, and therefore when the louver is opened, grain will begin falling through the louvers but the pile will remain above the louver.
When the louver is open by action of the sensor, enough grain will have accumulated on top of the louver to establish a choke load in the metering unit that is sufficient to block any air from rising up through the louver as the choke load of grain passes by the louver. The quantity of grain passing through the louver is sufficient to generally fill the entire opening of the louver, and therefore dust within the grain bin will be blocked from rising up through the open louver. This device operates well when the flow rate of grain from a truck is relatively low, such as when the grain is dumped from the truck through a relatively small outlet.
However, when the grain is dumped at a relatively large flow rate, such as when the entire tailgate of the truck is opened and the bed of the truck is tilted up to unload the truck, this device will cause a very large pile of grain to accumulate above the louvers. The metering units only allow grain through the louvers at a certain rate of flow, and when the flow rate out of the truck greatly exceeds the maximum flow rate that can pass through the louvers then a relatively large pile of grain will accumulate on top of the metering units. The truck may be emptied at such a quick rate that the resulting pile would be wider than the opening in the top of the grain bin. This would require manually shoveling or sweeping the grain back on top of the grain bin. It would be generally impractical to build a bin with a large enough opening and with enough metering units to accommodate the high flow rates resulting from dumping a large truck with the entire tailgate open.
It would therefore be desirable to provide a mechanism for reducing the amount of dust emitted from a grain bin when the grain is being dumped at relatively high flow rates such as when grain is dumped from a truck with the entire tailgate open and the truck bed tilted up. It would be desirable for such a mechanism to reduce emissions of grain dust during both high and low flow rate modes of operation. It would also be desirable for such a mechanism to be adapted for use with dust reduction mechanisms utilizing metering units as described above.